1. Field of the Invention
The present invention relates to sample vial handling apparatus and, more particularly, to apparatus for guiding and stabilizing the movement of sample vials into position at an operating station. The invention is particularly suited for handling vials which, after stabilization at the operating station, are transferred vertically from the station, operated upon, and then returned along the vertical path to the station.
2. Description of the Prior Art
U.S. Patent Applications Nos. 754,815 (Kampf) and 754,814 (Kampf et al.), filed Dec. 27, 1976, for SAMPLE HANDLING APPARATUS, and U.S. Pat. No. 3,859,528 (Luitweiler, Jr. et al.) all assigned to the assignee of the present invention, illustrate prior commercial sample handling apparatus for scintillation spectrometers such as gamma counters or liquid scintillation counters. In the illustrated apparatus, a plurality of sample vials are circulated past an operating station. The vials are supported within respective compartments of multi-compartment sample holders, and the holders are circulated in rectilinear fashion around the sample storage compartment of the apparatus past the operating station. At the operating station an elevator engages the bottom of a vial, drives the vial vertically upward out of the holder compartment through a vertical passage into a radiation measuring chamber for analysis, and thereafter lowers the vial back into the compartment. The sample holder is then indexed laterally to position a next vial at the station and the next vial is removed, measured, and returned in similar fashion.
Malfunctions of the foregoing apparatus have occurred when a sample vial jams between the sample holder and measuring chamber during its vertical travel. To minimize vial jamming, the vial, the vial holder, and the vertical passage into the measuring chamber are suitably dimensioned and configured to stabilize and guide the vial during vertical movement. For example, the opening of the vertical passage is disposed above and relatively close to the top of a vial at the operating station and is flared outwardly and downwardly to provide a guiding and camming surface for guiding a vial into the vertical passage. Consequently, even if a vial is slightly tilted or misaligned at the operating station, it will still in most cases be successfully elevated to the detection chamber.
Unfortunately, while the flared opening in the vertical passage assists in guiding the vial during upward movement, it increases the likelihood of jamming on the return trip of the vial from the measuring chamber to the sample holder. In this regard, as the vial is lowered it is possible for the bottom of the vial to shift laterally away from the vertical after leaving the vertical passage and before reaching the sample holder. If this occurs, the vial bottom can strike and jam on the top of the sample holder without entering the proper sample compartment. In an effort to minimize such possibility, the apparatus in the foregoing applications includes a stabilizing mechanism for stabilizing the sample holder at the operating station to at least prevent the holder from being misaligned. However, even an accurately stabilized holder cannot prevent the described jamming of a laterally shifted vial.
In U.S. Patent No. 3,270,202 (Long et al.), a sample vial at an operating station is guided vertically upwardly into a detection chamber by an enshrouding cylindrical hood which surrounds the vial at the operating station. The hood is normally recessed upwardly into the shield or well of the detection chamber. With the hood thus recessed, a sample vial is horizontally moved into position at the operating station beneath the detection chamber. With the sample thus positioned, the hood is then lowered from the well to surround the sample vial and hence provide a circumscribing channel for guiding the vial upwardly into the chamber. After a measuring operation, the vial is lowered to the operating station through the hood. With the vial thus returned to its holder, the hood is retracted to permit horizontal movement of the vial away from the operating station.
While the Long et al. apparatus does function satisfactorily to guide the sample vials during vertical movement, it has several disadvantages which reduce its attractiveness for use in commercial instrumentation. In this regard, the Long apparatus requires a separate motor, transmission, rack and pinion gearing, microswitches, and a relay holding circuit for controlling the vertical travel of the enshrouding hood. Consequently, the mechanical and electrical complexity and the cost of such a system become limiting factors in its use. As a result, a need exists for a sample vial guide which can accommodate horizontal movement of a sample vial into and out of an operative position and vertical movement to and from the operative position without the need for the complex control arrangement of the prior art. The present invention fulfills these needs.